Radio active electrode construction



July 21, 1959 K. LEHOVEC 2,896,137

RADIO ACTIVE ELECTRODE CONSTRUCTION Filed June 25, 1953 INVENTOR. KURTLEHOVEO BY 5 ms A 'roausvs United States Patent RADIO ACTIVE ELECTRODECONSTRUCTION Kurt Lehovec, Williamstown, Mass., assignor to SpragueElectric Company, North Adams, Mass., a corporation of MassachusettsApplication June 25, 1953, Serial No. 364,006

3 Claims. (Cl. 317-235) The present invention relates to a new andimproved type of electrode construction which is primarily useful withtransistors.

One type of transistor consists of a body of a semiconductive materialto which there is attached a low resistance electrode, and against whichis pressed two other point contacts termed the emitter and thecollector, re spectively. There is a need for improving theeffectiveness of either or both of these last electrodes. In order toaccomplish such ends, forming procedures, such as are mentioned in theWallace Patent No. 2,563,503, have been recommended particularly for thecollector electrode. While such procedures are elfective, they,nevertheless, do not provide point contact arrangements of the desiredeffectiveness.

It is an object of the instant invention to improve upon the aforegoingand related prior art. A further object of the invention is tomanufacture highly eflicient transistors. These and other objects of theinvention, as well as its advantages will be apparent from thisdescription, the accompanying claims, as Well as the accompanyingdrawmg.

This drawing diagrammatically shows the type of construction employedwith the instant invention.

This consists primarily of a body of a semi-conductive material 10, suchas, for example, n-type germanium, which has been provided on onesurface with a low resistance metallic layer 11, such as, for example, arhodium layer of from 0.0001 to 0.01 inch in thickness by plating.Against another surface of the semi-conductive body 10, two wireelectrodes 12 and 13 are positioned in accordance with known procedures.

At least one of these two electrodes 12 and 13 used with the presentinvention differs from the prior art probes in that it is provided witha source of alpha particles so as to bombard the adjacent surface of thesemiconductor with the same particles in order to alter the type ofconduction of the semi-conductor. Preferably, the semi-conductors usedwith the present invention are of the n-type germanium, and a p-njunction is formed adjacent to the electrodes by bombardment from thealpha particle source.

The source of alpha particles is, of course, capable of variation. Apreferred source is polonium metal which has been plated upon theexternal surface of the Wire probe. Alternately, the probes can consistof a substantially hollow tube, the center of which is filled with thesame metal or another type of source.

It has been known for quite some time that the electrical conductivityof a semi-conductor could be altered by particle bombardment. As anexample of this reference is made to the Lark-Horovitz Patent No.2,588,254, relating to a device comprising a unitary body of germaniumhaving a plurality of p-n type junctions through:

2,896,137, Patented July 21, 1959 out its length. Reference is also madeto the text Semi-Conductor Materials published in 1951 by AcademicPress, Inc., of New York. On page 66 of this last reference alphaparticles, deuterons, neutrons, and fast electrons are indicated astypes of radiation which can change n-type germanium to p-typegermanium, and which can increase the conductivity of the p-typegermanium. Nowhere in any of these or other references is there anyindication that a thin layer could be created adjacent to point contactsby the means described.

It will be realized by those skilled in the art that the inclusion of analpha particle source upon the collector of the transistor utilizing ann-type germanium body serves to create a p-n boundary close to thecollector probe. The depth of this boundary varies with the quantity ofalpha particles available for bombardment. Thus, it is believed that thebeneficial results of the present invention are similar to the resultsobtained by electrical forming of the collector of a transistor. It willbe further realized by those skilled in the art that this separateforming step is not necessary with the particular constructions hereinset forth, and that the described units can be easily and convenientlyproduced on a mass production scale.

Further, those skilled in the art will realize that the invention is notlimited to the use of polonium as an alpha particle source. Othersources, such as thorium, thorium carbide, and the like, can also beused. Similarly, other semi-conductive materials besides germanium, suchas, for example, silicon or silicon carbide can be used with theinvention.

As many apparently widely different embodiments of my invention may bemade without departing from the spirit and scope hereof, it is to beunderstood that my invention is not limited to the specific embodimentshereof except as defined in the appended claims.

What is claimed is:

1. In a point-contact transistor having a body of n-type conductivity, abase electrode in ohmic contact with said body, an emitter electrode inrectifying contact with said body, and a collector electrode in contactwith said body in close proximity to said emitter electrode; theimprovement comprising providing said collector electrode with a sourceof alpha-particle radiation so as to produce a region of p-typeconductivity in said body surrounding said collector contact.

2. A wire probe for a transistor which comprises a central conductivecore around which is plated a thin layer of polonium.

3. A transistor comprising a body of n-type germanium, a low resistancebase electrode attached to said body, and a wire probe bearing againstsaid body, said wire probe being plated with a layer ofalpha-particleemitting polonium to create a permanent pn junction withinthe germanium adjacent to said probe.

References Cited in the file of this patent UNITED STATES PATENTS2,563,503 Wallace Aug. 7, 1951 2,586,080 Pfann Feb. 19, 1952 2,604,496Hunter July 22, 1952 2,641,639 Slade June 9, 1953 2,651,009 Meyer Sept.1, 1953 2,666,814 Shockley Jan. 19, 1954 FOREIGN PATENTS 434,133 GermanySept. 22, 1926

